Scroll down to the bottom half of the page - look for this heading:
The Sabellidae with non-calcareous tubes

Could also be:
"The tall structure is a foraminiferan. They are acellular organisms that build a skeletal structure out of sand grains. In some tropical areas these are often found near sponges and build their structures out of sponge spicules. They have the name of "spicule trees."

The crustacean in the adjacent tube is indeed a filter feeder. It is also an amphipod.

These sorts of critters are common in the real world, pretty uncommon in tanks."